Love your explanation JY! :D

Premise 1: laughter --> aid recovery from illness (=gains in immune system)

Premise 2: tendency to laugh --> greater gains in immune system

Conclusion: [greater tendency + laugh less] > [less tendency + laugh greater]

First notice that there are two factors influencing the gains in immune system: laughter, and tendency.

Stimulus indicates that the second factor (innate tendency) exerts greater influence than the first factor; ("But much greater gains in immune system...")

This argument seems sound at the first glance since stim said tendency's influence is greater than that of laughter, and the conclusion correctly weighs more heavily the tendency factor compared to the laughter factor.

However, the unwarranted assumption made when reaching this conclusion is that the two factors are separate.

Notice "But" at the beginning of the third sentence. The argument can break down into something that looks like:

Laughter can increase immune system. --property 1

BUT tendency to laugh leads to greater increase in immune system.--property 2

Therefore, people who have a greater tendency to laugh, although they laugh little,

are helped more than people who have a less tendency, even if they laugh greater when watching the comic video.--basically a comparative statement weighing the strength of influence between tendency factor and actual laughter factor

The stimulus is trying to lure us into thinking that property 1 and property 2 are totally separate/ that we can weigh the strength of laughter & tendency.

But what if these two properties are compatible? In other words, what if a person who has a greater tendency to laugh (property 2) also laughs greater when shown comic videos (property 1)? Then we cannot draw any comparison between property 1 and property 2 as to which factor leads to more gains in immune system.

This is what answer choice (A) says --> it ignores the situation where a person who has a greater tendency is the person who also laughs greater when shown comic videos.

I might be wrong so JY or anyone please correct me!

I am going to give it a try.

(abbreviation:

apc - adequate prenatal care

lbw - low birth weight)

Conclusion: apc reduces the risk of lbw

why? (the one premise that is directly related to supporting our conclusion): mothers with apc are less likely to have lbw babies

context premise: babies born prematurely more likely to be lbw

Disregard the context premise for now.

If you still remember JY's excellent Goku-blue beam-car analogy,

Goku (P): records indicating that mothers with apc are less likely to have lbw babies

Car (C): apc reduces the risk of lbw

the subtle, hidden blue beam here is that:

the hospital record actually did classify those with apc as apc. (in other words, if a mother is indicated as having had apc, then she really did receive apc)

Answer choice (B) thins out this blue beam. The hospitals routinely classify those mothers as apc whenever the record is not available. This means that even if some mothers were labeled as apc, they did not in the reality received apc. Hospitals were just too lazy to figure out the truth.

Now, the part "mothers giving birth prematurely" in this answer choice doesn't really matter. Whether the answer choice says 'mother who gave premature birth' or 'mother who gave lbw babies' doesn't really matter because the blue beam supporting the Goku premise--records indicating that mothers with apc are less likely to have lbw babies--is already destroyed.

* Why (D) is wrong:

Think of it this way:

(D) Some babies not born prematurely, (whose mothers received adequate prenatal care), have low birth weights.

If you read this answer choice excluding the part in the parenthesis, it's only talking about the relationship between premature babies and lbw. This doesn't have any bearing on our conclusion, which involves apc.

Now if you try to link up "some babies not born prematurely" with the part inside parenthesis, look how there is no relationship established between these two. We cannot infer anything between prematurity and apc.

Hey Christian, thank you so much for the kind explanation!

So if 'some' suffices to weaken an argument-- what about #8 in pt 53 in section 1? Answer choice E says "...several of the children who had slept with night-lights as infants were near sighted." This one does not weaken the argument because it is only several (some)

I read a comment that 'several' here is not the problem but that we don't know if this nearsightedness is caused by the night lights.

If this answer choice included a phrase that said something like "several of the chilren who had slept with night lights whose nearsightedness is caused by sleeping with night lights on" then could this answer choice wreck the argument, even if it is only some?

I am really confused.

Thanks for your input!

Thanks! Let's hope for the best & keep the momentum going!

Just because a person has made a bad argument is not enough of a reason to reject the conclusion!